In 2009, Bethesda Softworks bought id Software, creators of countless games and also owners of the advanced id Tech 5 engine. For Skyrim, however, they still chose to use their own Creation Engine. Today, John Carmack told Gamasutra that id Tech 5 would be 'unacceptable' for Skyrim:

"The megatexture direction [in id Tech 5] has some big wins, but it's also fairly restrictive on certain types of games'; [and] it would be a completely unacceptable engine to do Skyrim in, where you've got the whole world, walking across these huge areas."